|Michael J Fox|
The 50-year-old actor was replaced by Charlie on 'Spin City' 10 years ago after he was diagnosed with Parkinson's disease and the pair became friends.
Michael was concerned about Charlie's state of mind after he was fired from the comedy TV series in the wake of his drug use and erratic behaviour, but thinks he's doing well now.
During an appearance on the 'Late Show with David Letterman' he was asked how Charlie was doing, to which he replied: "Well I feel bad for him with all his troubles now … but he's doing OK, so who am I to say he's not?"
Although Charlie appears to be more eccentric than most, Michael believes everyone who works in showbusiness is a bit crazy.
He said: "Showbusiness: We're all here because we're not all there!"
Michael appeared on the chat show to promote the 2011 Nike Mags sneakers – which are based on the futuristic pair of self-fastening shoes the actor's character Marty McFly wore in 'Back to the Future Part II'.
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The sneakers are available to buy from eBay and all proceeds will be given to the Michael J. Fox Foundation for Parkinson's Research.